With just over an hour remaining, the Space X company called off Monday's planned launch because of a rocket leak. A new launch date was not set; the next opportunity would be Friday.

Officials said a helium leak in the first-stage of the unmanned Falcon rocket forced the postponement. The launch already had been delayed a full month for various reasons.

Over the weekend, NASA almost postponed the launch because of a computer outage at the International Space Station. But it decided Sunday that everything would be safe for the arrival of the Dragon capsule and its 2½ tons of supplies.

The computer, a critical backup, failed outside the space station Friday as flight controllers were trying to activate it for a routine software load.

It's the first breakdown ever of one of these so-called space station MDMs, or multiplexer-demultiplexers, used to route computer commands for a wide variety of systems. Forty-five MDMs are scattered around the orbiting lab. The failed one is located outside and therefore will require spacewalking repairs.

The Dragon capsule holds a gasket-like material for next week's computer replacement. This new material was rushed to the launch site over the weekend and loaded into the Dragon.

NASA astronauts Rick Mastracchio and Steven Swanson will perform the spacewalk next Tuesday — regardless of whether the Dragon flies by then. It will take several days to get the replacement computer ready for installing, thus the one-week wait before the job, NASA's Kenny Todd, a station operations manager, said Monday.

SpaceX — Space Exploration Technologies Corp. of California — is one of two American companies hired by NASA to fill the cargo gap left when the space shuttles retired in 2011. Orbital Sciences Corp. of Virginia is the other.